Photoluminescence investigation of Superlattice Ordering in Organometallic Vapour Phase Epitaxy grown InGaP Layers

InGaP alloys, lattice matched to GaAs (100), were grown in different organometallic vapour phase epitaxy reactors operating at low pressure. cw-photoluminescence spectroscopy was used to investigate the role of growth temperature, substrate misorientation and doping on the ordering effect. The bleaching of the exciton peak and a strong thermal quenching of the PL efficiency was observed in different samples. The line-shape analysis of PL spectra obtained at different temperatures and excitation intensities confirmed the band gap dependence on the ordering effect; a maximum band gap reduction (BGR) of 109 meV was observed, corresponding to an order parameter =0.47, obtained for nominally undoped layers grown at 640 °C on GaAs (100) substrates, 2° misoriented toward the (110) direction. A weak dependence of such maximum on degree and direction of the substrate misorientation seems to be possible; the temperature dependence of the PL peaks resulted the weaker the higher the ordering presence. In the case of both n- and p-type doped InGaP layers, the effect of doping in reducing both the ordering formation and the average size of ordered domains was confirmed.